An ultrasound apparatus for determining bladder volume is shown in U.S. Pat. No. 4,926,871, in the name of Dipankar Ganguly et al. That apparatus, involving an automatic calculation of bladder volume from ultrasound measurements of the major axis of the bladder and an axis perpendicular thereto, requires an operator to manipulate the scanhead transducer in a particular way to obtain the ultrasound measurements. An ellipsoid model is used as the basis for calculating bladder volume from the ultrasound measurements. The apparatus furthermore is used to determine bladder volume on an event-by-event basis and does not accumulate information from which long-term patterns or an accurate patient history could be developed. In addition to the above-mentioned apparatus, there are other sophisticated medical ultrasound machines which could be used to measure bladder volume, but these are typically limited to a single imaging plane (B-mode scanning) and require an operator to obtain the necessary ultrasound information. In addition, the bladder outline would have to be determined from that ultrasound information and then the volume calculations performed. Such a capability is not currently available on any medical ultrasound machine.
In addition to obtaining accurate bladder volume event information, it is desirable to have a bladder volume instrument which is completely automatic and which can be conveniently carried on the person of the user, so that historical information on bladder volume can be developed on a continuing basis.